1. Field of the Invention
The present invention is directed to porous groyne-like structures and method for their use in reclaiming beaches, shoreline areas and other land masses which are subject to erosion by natural forces and, more specifically, to permanent and semi-permanent groyne structures which may be left in place when deployed. In some embodiments the groynes may be systematically raised as reclamation progresses from the buildup of silt, sand, shells, dirt, twigs and branches, grasses and other materials.
2. Description of Related Art
Beach and other shoreline erosion, especially in coastal areas, is a major concern to property owners who have residences or establishments which are situated in close proximity to the shoreline. Not only is there a tremendous personal and economic loss caused by damage to, or loss of, real estate, housing and commercial buildings by shoreline or beach erosion, but there is also recreational loss of waterfront property which adversely affects the general public.
To deter coastal erosion in many areas, large seawalls are constructed to prevent high tides from reaching land and property. Such structures are costly and are only practical when population densities make it economically reasonable to construct them. Further, such structures have an adverse effect on the natural appearance of the shoreline and, in many areas, cannot be practically constructed.
Other methods of shoreline reclamation include creating jetties or artificial barriers or reefs which extend from the shoreline. These structures are permanent installations and are generally utilized to prevent sand along coastal areas from washing out to sea or filling in inlets and the like by wave action. Like seawalls, however, such structures are costly to construct and maintain and, in some areas, are not appropriate for use due to the shoreline configuration, prevailing currents or tidal activity and the like. Also, such structures create a safety hazard in areas where recreational activity is anticipated.
A further method for reclaiming shoreline areas and preventing erosion is the placement of off-shore, underwater barriers. Often, large porous structures are placed along a sea floor or riverbed at some distance from the existing shoreline. The structures are provided to break wave, current or tidal action thereby creating a zone of low velocity water flow adjacent a beach or riverbank so that sand, silt and other particulate material will settle out of the water before being conveyed by fluid currents out from the shoreline. Again, such outer barriers are only appropriately used in some locations and are not appropriate for use in many locations and may be objectionable for use in some areas due to the adverse affect on aquatic life.
Other methods which are widely used to reclaim shorelines or beaches are dredging and sand impartation. When major dunes along a shoreline are damaged or washed away during heavy storms, it is often necessary to import new dirt and sand to re-establish the dunes to provide a natural barrier to tidal activity. Dredgers are commonly utilized to pump sand from a sea floor or riverbed to build up natural barriers. Such methods of shoreline reclamation, however, are temporary measures, at best, and do not provide a long-term solution to shoreline erosion. Further, such restoration methods are extremely costly and are not practical in many locations.
In view of the foregoing, there is a need to provide a method and apparatus for economically reclaiming damaged shorelines, and other land mass beach areas which can be practically used without an adverse effect to either land or water environments. In U.S. Pat. Nos. 1,969,123 and 4,710,056, methods and structures for beach restoration are disclosed which utilize netting for purposes of trapping sand, shells and other particulate matter carried by wave action. Nets are extended outwardly from the shoreline and are left in place until a buildup of sand and other particulate matter is established after which the nets, which may be buried several feet or more in the newly collected material, are withdrawn by winches or other means. The removal of the netting material can adversely affect the restored shoreline by creating trenches or furrows which form natural channels in which water flows away from the shoreline thereby conveying particulate matter back to a body of water.
In prior U.S. Pat. Nos. 5,720,573 and 5,944,443, screen or netting structures for groynes are disclosed wherein the screens are periodically raised as material is deposited during reclamation so as to reduce interference with newly deposited materials. During use, flexible materials such as screening and netting are effective for material build-up, however, under some deployment conditions such as during violent storms and sea surges, such groyne structures can be significantly damaged. Damage to screening or netting mandates added cost for required repair and replacement in order to maintain an effective groyne system.
Also, many groyne systems, such as described in the aforementioned patents, are specifically designed to be removably deployed. In some areas, such as along coastal or other shorelines it may be more beneficial to deploy or erect groyne systems which are designed to be semi-permanent or permanent. Such groyne systems must be constructed to with stand the forces encountered including wind, wave and tidal action over extended periods of time.